Compact incinerator

ABSTRACT

A compact incinerator including a longitudinally extending furnace having a solids inlet and residue outlet, and heaters disposed around the furnace peripheral surface. A conveyor located inside the furnace moves solid matter from the inlet along the furnace length and the heaters simultaneously cause conbustion of solids during such movement prior to discharge as ash through the outlet. Preheated 0air supplied to the furnace aids combustion and carries away volatile gases generated during the combustion process. To assure complete burning of all gases, the gases and air are circulated through an afterburner mounted on the furnace prior to discharge to the atmosphere.

United States Patent 11 1 Turner Nov, 27, 1973 COMPACT INCINERATOR2,932,713 4/1960 Powers 110/8 x [75] Inventor: Abner B. Turner,Greensburg, Pa 3,471,369 10/1969 Cox et al. 110 10 x [73] Assignee:Westinghouse Electric Corporation, Primary Examinerl(enneth W. Sprague17.7,] Mlml' Jim. 3|, I972 {211 App]. No.: 221,991

[52] US. Cl. 110/8 R, 110/8 A, llO/ll,

[51] Int. Cl. F23g 5/12 [58] Field of Search 110/8 R, 8 A, 8 E,

110/10, ll, 15, 18 E.

[56] References Cited UNITED STATES PATENTS 3,648,630 3/1972 Hobbs et a1110/8 3,491,707 H1970 Bakker 110/8 3,362,887 1/1968 Rodgers llO/ll X3,027,445 3/1962 Johnson llO/8 X 7 Pittsburgh, Pa.

Attorney-14, T. Stratton et al.

[57] ABSTRACT A compact incinerator including a longitudinally extendingfurnace having a solids inlet and residue outlet, and heaters disposedaround the furnace peripheral surface. A conveyor located inside thefurnace moves solid matter from the inlet along the furnace length andthe heaters simultaneously cause conbustion of solids during suchmovement prior to discharge as ash through the outlet. Preheated Oairsupplied to the furnace aids combustion and carries away volatile gasesgenerated during the combustion process. To assure complete burning ofall gases, the gases and air are circulated through an afterburnermounted on the furnace prior to discharge to the atmosphere.

5 Claims, 4 Drawing Figures SOLIDS PATENTED "BY 27 ms SHEET 10F 2 mQjOwCOMPACT INCINERATOR BACKGROUND OF THE INVENTION The invention describedherein relates to wastewater treatment apparatus and more particularlyto a compact incinerator designed to dispose of solid matter separatedfrom liquid in a sewage or other solids processing system.

The products resulting from treatment of organic or inorganic materialsin industrial and commercial processes, often include a liquid havingsolid components therein which cannot be discharged directly to a streamor river.

As a result, many different processes have been developed for disposingof the solids. One well known method involves incineration wherein thesolids are burned and the ash residue disposed of in a conventionalmanner. incinerators are extensively used in large industrial operationsand the more recent development of small sewage disposal plants of thetype used on boats or small ships, for example, have concurrently led todesigns of low volume incinerators. To achieve economy in operation,known small sewage plants store solid matter which then is burned in anan incinerator at infrequent intervals each day.

The disadvantages in such designs are that the solids compact and losemoisture and the aggregate tends to solidify to a degree such thatparticle separation which is necessary for efficient combustion does nottake place. Subsequent to burning, the residue then comprises ash whichmay be disposed of but the incompletely burned solids must be reburnedor otherwise reduced to a state where they may properly be discarded.Further, to assure complete combustion of the solid products, theburners could of course be operated on a 24 hour basis but doing sorequires relatively large storage facilities for the fuel where space isat a premium. Also, the constant application of heat to the incineratorresults in high cost and therefore uneconomical operation because littleor no solid matter would be run through the incinerator during off peakhours.

BRIEF SUMMARY OF THE INVENTION A compact incinerator which exposes solidparticulate matter to a temperature and for a time necessary to efiectcomplete combustion of the solids as they are advanced by a conveyoralong the incinerator length, and then discharges the residue to acollector. The incinerator includes integral structure which preheatsair used to support combustion and to carry both the burned and unburnedgaseous products of combustion to an afterburner located in theincinerator outlet. In a preferred form, the unburned gases may beconsumed by the afterburner which derives its heat from the incineratoror from a separate heater located in the gas flow path to theatmosphere. It will occur to those skilled in the art that differenttypes of solids conveying devices may be used for moving the solidconstituents through the incinerator and for burning or chemicallyabsorbing the gases discharged to the atmosphere.

It therefore is an object of the invention to provide an incineratoroperating at a temperature chosen to correspond with the time requiredto burn solid matter as it moves along the incinerator length.

Another object of the invention is the provision of an incinerator whichutilizes its radiated heat to preheat air introduced into theincinerator for supporting com- -tile gases not burned in theincinerator prior to their discharge to the atmosphere; and

Another object of the invention is to provide an incinerator of compactdesign which is efficient and economical to construct and operate.

BRIEF DESCRIPTION OF THE DRAWING While the specification concludes withclaims particularly pointing out'and distinctly claiming the subjectmatter of the invention, it is believed the invention will be betterunderstood from the following description taken in conjunction with theaccompanying drawing, wherein:

FIG. 1 is a view in elevation, partly in section, of the incinerator ofthis invention;

FIG. 2 is a side view of the incinerator illustrated in FIG. 1;

FIG. 3 is a view in elevation, partly in section, of a modification ofthe incinerator shown in FIG. I; and

FIG. 4 is a side view of the incinerator of FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawingswherein like reference characters designate like or corresponding partsthroughout the several views, there is shown in FIG. I, an incinerator10 designed to burn solid particulate matter preferably of the kindwhich is separated from a liquid during a liquid treatment operation.The incinerator is mounted on a base 12 which supports a furnace 14having a solids inlet 16 which deposits solid matter on a screw typeconveyor 18. The conveyor is designed to move the solids longitudinallythrough the furnace prior to discharge through an outlet 20 to an ashcollector 22. Combustion of the solids is accomplished through themedium of electrically operated heaters 24 preferably disposed on thelower half of the furnace outer peripheral surface. To supportcombustion, air introduced through an inlet 26 flows along the length ofthe furnace, asshown by the arrows, to be preheated prior to enteringthe furnace through an inlet 28. During its course of travel through thefurnace, the air serves the dual function of supporting combustion andcarrying away gaseous products of combustion, in-

cluding any volatile gases not burned in the furnace.

This gas mixture then flows through outlet 30 into a gas burning spaceor afterburner 32 before being discharged through the furnace outlet 34to the atmosphere.

Considering the design in greater detail, the base 12 may be supportedby stanchions 36, for example, which are mounted on or adjacent othercomponents in the waste-water treatment system. The furnace 14 is ofcylindrical configuration with both the solids inlet 16 and air inlet 28being located on one end to permit solids and airflow in the samedirection longitudinally of the furnace prior to being dischargedthrough their respective outlets 20 and 30.

The screw-type conveyor 18 includes a helical metallic strip 38 weldedor otherwise secured to the tube 40 by radially extending brackets 42.As shown, its inner peripheral edge is spaced a substantial distancefrom 'tube 40 while its outer edge forms a close fit with the roundinner walls of the furnace. As the furnace is heated to about 800 to1,000F, depending on the solids being burned, the parts will thermallygrow such that the strip outer edges will just barely contact thefurance walls and thus effectively move the solids along the furnacelength. The opposite ends of hollow tube 40 are supported by a pair ofshafts 44 which rotate in bearings 46 disposed in an end plate 48attached to opposite sides of the furnace. Rotation of the helical stripconveyor 38 is accomplished by a motor 50 and gear reducing unit 52which is directly coupled to the shaft 44.

Heat for combustion purposes may be supplied to the furnace in anyone ofa number of different ways and in the embodiment shown, the heaters 24are of a semicylindrical shape and are attached to the lower half of thefurnace by straps 54, FIG. 2, or other conventional securing means. Theheaters are commercially available and generally consist of amultiplicity of conductors embedded in a ceramic or asbestos-likeelement designed to conform to the furnace outer surface. Heat thereforeis transmitted to the combustion space by conduction through the furnacewalls.

In order to acquire efficient combustion economically, the incoming airis preheated by the residuum of heat from the furnace. This isaccomplished by enclosing the furnace in heavy steel plates orinsulating plates such as transite, 56 and 58 to form a plenum chamber59. Since the air inlet 26 is located on the opposite end from thesolids inlet to the furnace, the incoming air must flow longitudinallythrough the plenum chamber prior to being introduced into the furnacethrough inlet 28. In so doing, the air is preheated by the furnaceresidual heat therefore eliminating the need to provide a separate heatenergy source which otherwise would be required to heat the air to helpsupport the combustion process. The heaters 24 are chosen to raise thefurnace temperature to approximately 1,000F and the heat thus impartedto the furnace atmosphere, combined with the preheated air flowingtherethrough, helps assure complete reduction of the solid matter toashes.

During the course of flow through the furnace, preheated" air alsopurges the furnace of all volatile and non-volatile gases includingthose which have not been consumed during the solids burning process.The remaining air, combustion products volatile and nonvolatile gasesare then discharged to an afterbumer chamber 32 which is formed by theouter walls of the furnace and a semi-spherical element 62 having itsends placed in direct contact therewith. Since the temperature infurnace 14 is maintained at a relatively constant temperature betweenabout 800 and 1,000 F, it is apparent that the temperature in afterbumerchamber 32 ranges between about 600 and 800F. This temperature issufficient to burn most gases discharged thereinto from the furnace 14.Should complete combustion of all gases and elimination of odors at thedischarge outlet be desired, a supplemental heater 63 may be energizedto raise the temperature in chamber 32 to about l,400 F. Upon completionof the total combus tion process, the remaining air and gaseouscombustion products flow to the atmosphere, or to carbon filters,through outlet 34. In some installations, natural convection currentsmay be relied on for moving the air through the furnace and theassociated chambers prior to discharge to the atmosphere. However, itmay be desirable to mount a fan or air blower 63 on the inlet 26 topositively induce the circulation of the air through the incinerator.

In operation, heating elements 24 heat the furnace to 800l,000 Fdepending on the character of solids to be consumed, at which timesolids may be introduced into the furnace through inlet 16.Simultaneously preheated air flows throughinlet 28 to the furnace forproviding the oxygen necessary for combustion purposes. As the solidsare moved longitudinally or axially of the furnace by the rotatinghelical conveyor, steam and gases are driven from the solids and theremaining solid particles are then completely burned to provide an ashwhich is then deposited by the conveyor in ash container 22. The gaseousproducts of combustion including air and those gases not burned in thefurnace are then circulated through high temperature chamber 32 to helpassure complete combustion of the gases prior ,to their dischargethrough outlet 34 to the atmosphere.

The residence time of solids in the furnace desirably should correspondwith temperature to achieve efficient and economical operation. The typeof solids being burned determines the furnace temperature and in thecase of sewage, the desired temperature range is 800 to l,O00 F. For afurnace combustion space of about 680 cu. in., i.e. 24 inches long and 6inches diameter, the helical conveyor should rotate at one-half rpm,thus providing a residence time of 12 minutes in the furnace. Thisillustrative time-temperature relationship assures complete reduction ofthe solids to ashes.

Since provision is made for consuming unburned circulating arrangement.As shown, instead of utilizing ceramic types of heating elements, stripheaters 70 are mounted on the outside peripheral surface of the furnaceand upon being energized, transmit by conduction heat through thefurnace wall into the combustion space. In both embodiments disclosedherein, appropriate and well known temeprature sensing elements may belocated inside the furnace and connected to control means for energizingthe space heaters to thereby maintain the temperature within the furnaceat predetermined levels. As in the embodiment of FIG. 1, the

' space heaters may be located and positioned only par tially around thefurnace and their spacing along the furnace length may be varied'toprovide the proper temperature profile for obtaining the most efficientoperation and maximum combustion of the solids material which is movedtherethrough.

To provide preheated air for combustion, plates 72 are attached to thetop and sides of the furnace and nace, it is discharged into an exhauststack 74 having a heating element 76 positioned therein. The element ispreferably mounted at an angle to the axis of the stack so that air andgaseous products of combustion leaving the furnace are required to flowacross the heating element and thus assure .combustion of any gaseswhich have not been consumed in the furnace. After the gases are burned,the air is then discharged to the atmosphere in a conventional manner.

The draft provided by the exhaust gases blowing out the stack usually ismore than sufficient for moving preheated air through the combustionchamber. Control over preheated air velocity may be accomplished bycating a damper in the exhaust stack in a conventional manner. Byutilizing this kind of arrangement, the furnace is assured of having thedesired quantity and temperature of air which is necessary to aid in thedecomposition and combustion of the solid particles as they are movedthrough the furnace by the helical conveyor 38.

In view of the above it will be apparent that many modifications andvariations in the invention may be made in light of the above teachings.It therefore is to be understood that within the scope of the appendedclaims, the invention may be practiced otherwise than as specificallydescribed.

I claim:

1. An incinerator for burning solid material comprising:

a furnace including a combustion chamber having heating means on thewalls thereof for providing heat for combustion, an inlet for solidparticulate matter and an outlet for discharge of the solid products ofcombustion;

a conveyor in said furnace arranged to move said solid matterlongitudinally toward the outlet, said conveyor comprising a shaftextending the length of said combustion chamber and having its endspositioned in bearings disposed on opposite end walls of the furnace, ahelically formed strap attached to opposite ends of the shaft whichmoves the solid matter from the inlet along the combustion chamberlength to said outlet;

drive means associated with said furnace for operatgases including theexcess air, products of combustion and gases generated during thecombustion process in the furnace; and

after-bumer means on said furnace connected tothe gas outlet, saidafter-bumer means comprising a housing mounted on said furnace, theinner wall surfaces of said housing defining with the furnace outerwalls a gas combustion chamber which extends substantially the completelength of the furnace and circumferentially encompasses a part of thefurnace upper wall surface, the arrangement being such that combustiongases discharged through the furnace gas outlet, pass through the gascombustion chamber which helps consume gases not burned in the fumaceduring the combustion process.

2. The incinerator according to claim 1 wherein supplemental heatingmeans is positioned in said gas combustion chamber to raise thetemperature therein to a level sufficient to assure combustionof allgases and elimination of odors which otherwise would be discharged tothe atmosphere.

3. The incinerator according to claim 1 wherein said afterbumer meanscomprises a housing enclosing at least a portion of said furnace to forma combustion chamber therebetween which acquires its heat by conductionthrough the walls of the furnace and means connecting the gas outletfrom said furnace with the chamber so that unburned gases from thefurnace may be consumed therein prior to discharge to the atmosphere,and

said preheating means comprises an enclosure over said housing to formtherebetween a space through which the incoming air to the furnace flowsto be preheated prior to its entry into the furnace.

4. The incinerator according to claim 1 wherein said heating meanscomprises strip heaters having their inner surface in direct contactwith the outer surface of said furnace and being of a size sufiicient toimpart heat to said furnace to completely burn said solids during theirresidence time in the furnace.

5. The incinerator according to claim 1 wherein an exhaust stackcommunicating with the furnace gas outlet is mounted on the end of saidfurnace; and

said afte rbumer means further includes a heating element in said stackover which the discharge gas from the furnace flows for burning anyunburned atmosphere.

1. An incinerator for burning solid material comprising: a furnaceincluding a combustion chamber having heating means on the walls thereoffor providing heat for combustion, an inlet for solid particulate matterand an outlet for discharge of the solid products of combustion; aconveyor in said furnace arranged to move said solid matterlongitudinally toward the outlet, said conveyor comprising a shaftextending the length of said combustion chamber and having its endspositioned in bearings disposed on opposite end walls of the furnace, ahelically formed strap attached to opposite ends of the shaft whichmoves the solid matter from the inlet along the combustion chamberlength to said outlet; drive means associated with said furnace foroperating the conveyor at a speed which corresponds to the residencetime required for solids to remain in the furnace to assure completecombustion of said solids; air preheating means on said furnace forraising the temperature of air supplied to said furnace to supportcombustion, and a gas outlet to discharge gases including the excessair, products of combustion and gases generated during the combustionprocess in the furnace; and after-burner means on said furnace connectedto the gas outlet, said after-burner means comprising a housing mountedon said furnace, the inner wall surfaces of said housing defining withthe furnace outer walls a gas combustion chamber which extendssubstantially the complete length of the furnace and circumferentiallyencompasses a part of the furnace upper wall surface, the arrangementbeing such that combustion gases discharged through the furnace gasoutlet, pass through the gas combustion chamber which helps consumegases not burned in the furnace during the combustion process.
 2. Theincinerator according to claim 1 wherein supplemental heating means ispositioned in said gas combustion chamber to raise the temperaturetherein to a level sufficient to assure combustion of all gases andelimination of odors which otherwise would be discharged to theatmosphere.
 3. The incinerator according to claim 1 wherein saidafterburner means comprises a housing enclosing at least a portion ofsaid furnace to form a gas combustion chamber therebetween whichacquires its heat by conduction through the walls of the furnace andmeans connecting the gas outlet from said furnace with the chamber sothat unburned gases from the furnace may be consumed therein prior todischarge to the atmosphere, and said preheating means comprises anenclosure over said housing to form therebetween a space through whichthe incoming air to the furnace flows to be preheated prior to its entryinto the furnace.
 4. The incinerator according to claim 1 wherein saidheating means comprises strip heaters having their inner surface indirect contact with the outer surface of said furnace and being of asize sufficient to impart heat to said furnace to completely burn saidsolids during their residence time in the furnace.
 5. The incineratoraccording to claim 1 wherein an exhaust stack communicating with thefurnace gas outlet is mounted on the end of said furnace; and saidafterburner means further includes a heating element in said stack overwhich the discharge gas from the furnace flows for burning any unburnedgases from the furnace before being vented to the atmosphere.